Recently, due to the fast development in electro-optic techniques, the related studies and techniques of the plasma display panel (to be abbreviated as PDP here below) have grown rapidly and compatible with multimedia applications. The advantages of PDP, in contrast to liquid crystal displays now in use, include better moving picture quality and image display characteristics. In addition, the thickness of a PDP is much thinner than that of a conventional cathode ray tube (CRT) television set. The PDP thus catches the eyes of scientists and researchers and have become a popular field of research. We believe that PDP will soon become popular for home use replacing the traditional CRT displays.
In general, one field for displaying one frame is divided to a plurality of sub-fields, and a PDP represents gray scale with sub-fields. That is, different light emission time of discharging in each sub-field is used to display different bright brightness of a pixel. Please refer to FIG. 1 showing the sequence of sub-fields used in the prior art. Typically, one field includes eight sub-fields ranging from SF.sub.0 to SF.sub.7, and the brightness levels of brightness are divided to 2.sup.8, that is, 256 grades. Each sub-field signal comprises an address period, a sustain period, and a reset period. The sustain periods of these sub-fields SF.sub.0, SF.sub.1, SF.sub.2, SF.sub.3, SF.sub.4, SF.sub.5, SF.sub.6, and SF.sub.7, are at a ratio of 1:2:4:8:16:32:64:128. The 256 intensity levels are achieved by selectively combining the sub-fields to turn the PDP on.
Nevertheless, the abrupt change of image brightness appears when the brightness level of the image is changed. For instance, a signal having a brightness level 128 is on the left of the emitting pattern and a signal having a brightness level 127 is on the right of the emitting picture. When an image is moved from left direction to right direction, the abrupt change of image brightness will appear and further lead to a dynamic false contour in a certain part of the image. Therefore, it is inconvenient and inefficient for applications and has a lot to be improved.